Pass data between C++ Eigen Matrix and MATLAB mxArray with a cell array

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I would like to pass data between Eigen Matrix/Vector and mex arrays. In the following code, I defined a mex array called y_output, which contains a cell array. The variable y_output will be passed to MATLAB. Each element in y_output is a vector but with different lengths. I would like to pass a pointer that points to Eigen vectors to the mex array y_output.
Notice that the data stored in y will be modified with a user-defined function. After calling the function, I would assume that the data stored in y_output will be modified corresponding. However, I cannot directly pass the pointer from y_output to y. Is there any way to make it possible? Thanks!
#include "mex.h"
#include "matrix.h"
#include <Eigen>
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
// prhs[0]: a cell array of length T, each element is a vector with different lengths
mwSize T = mxGetNumberOfElements(prhs[0]);
mwSize* n = new mwSize[T];
Eigen::VectorXd* z = new Eigen::VectorXd[T];
for(int t=0; t<T; t++){
n[t] = mxGetNumberOfElements(mxGetCell(prhs[0], t));
z[t] = Eigen::Map<Eigen::VectorXd>(mxGetPr(mxGetCell(prhs[0], t)), n[t]);
// create a cell matrix with T rows and one columns
mxArray* y_output = mxCreateCellMatrix(T,1);
// create corresponding Eigen objects
Eigen::VectorXd* y = new Eigen::VectorXd[T]();
Eigen::VectorXd y_temp(n[0]); y_temp.setZero();
for(int t=0; t<T; t++){
mxSetCell(y_output, t, mxCreateDoubleMatrix(n[t], 1, mxREAL));
y[t] = Eigen::VectorXd::Zero(n[t]);
Eigen::Map<Eigen::VectorXd> y[t](mxGetPr(mxGetCell(y_output, t)), n[t]); // This is not correct!
// Myfun(y, z); // y is modified
// set output
plhs[0] = y_output;

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